1. Field of the Invention
The present invention relates to a lens movement control method and a lens movement control apparatus of a camera module. More particularly, the present invention relates to a lens movement control method and a lens movement control apparatus of a camera module for preventing allophone of a Voice Coil Actuator (VCA).
2. Description of the Related Art
In cases where a camera module photographing a moving image or taking a picture is mounted in a portable terminal, a Voice Coil Actuator (VCA) has been widely used as the means to make a lens perform a linear motion for focusing.
FIG. 1 is a cross-sectional view illustrating a state of a VCA in a camera module when it is in an operation mode according to the related art. FIG. 2 is a cross-sectional view illustrating a state of a VCA in a camera module after a lens moves to a bottom surface according to the related art.
Referring to FIGS. 1 and 2, a VCA 120 engages with a side surface of a lens 110 to be located at an upper portion of a bobbin support 131 of a housing 130. The VCA 120 includes a permanent magnet 122 and a bobbin 121. When a camera module 100 is switched from a camera operation mode to a camera stop mode, power of the camera module 100 is turned-off. Accordingly, as shown in FIG. 2, the bobbin 121 moves the lens 110 to a bottom surface 133 by force of a spring 160. As illustrated above, when the lens 110 moves to the bottom surface 133, a VCA allophone is created when a lower end of the bobbin 121 collides with a bobbin support 131 of the housing 130.
A lens movement control operation of a camera module according to the related art will be described below with reference to a control block diagram of FIG. 3, and a lens movement control flowchart of FIG. 4.
FIG. 3 is a block diagram illustrating a camera module with a VCA according to the related art, and FIG. 4 is a flowchart illustrating a lens movement control method of a camera module for preventing an occurrence of a VCA allophone according to the related art.
Referring to FIGS. 3 and 4, a controller 103 determines whether a camera module is in a camera operation mode based on an input from an input unit 102 in step S11. If it is determined in step S11 that the camera module is not in the camera operation mode, the controller 103 returns to step S11. In contrast, if it is determined in step S11 that the camera module is in the camera operation mode, the controller 103 enters a camera stop mode in step S12.
The camera operation mode is a mode in which the camera module is performing a photographing operation. The camera operation mode includes a preview (i.e., a state displaying that a camera module is performing a photographing operation before taking a picture) or a photographing of a moving image. Furthermore, the camera stop mode is a mode in which the camera module stops a photographing operation. The camera stop mode includes a quick view (i.e., a state displaying a taken picture on a screen for a moment directly after taking a picture in a preview state), a menu view or a photograph view. Entering the camera stop mode may automatically be performed by a controller 103 like the quick view and may be performed as a result of an input into an input unit 102.
In step S13, the controller 130 sets a number (n) (the time it takes for a bobbin to drop, in seconds) of bobbin 121 drops to an initial value 0 and controls a lens driving unit 104 to drop a bobbin 121 in step S14. When the bobbin 121 starts to drop, the controller 103 increases the number (n) of bobbin 121 drops by 1 in step S15. Next, the controller 103 determines whether a lens 110 moves to a bottom surface 133 by using a detecting unit 105 in step S16. If it is determined in step S16 that the detecting unit 105 detects that the lens 110 moves to the bottom surface 133, the controller 103 controls a lens driving unit 104 to terminate lens movement. In contrast, if it is determined in step S16 that the lens 110 does not move to the bottom surface 133, the controller determines whether the number (n) of bobbin 121 drops is equal to 6 (a maximum number of time a bobbin may drop before power off of a camera module) in step S17. Although the maximum number of bobbin 121 drops is equal to 6 in this example, it is possible for it to be more than 7. If it is determined in step S17 that the bobbin dropping number is less than 6, the controller 103 returns to step S14 and repeats the process of dropping the bobbin 121. Accordingly, it is appreciated in the related art that the lens 110 slowly moves to the bottom surface 133. In contrast, if it is determined in step S17 that the number of bobbin 121 drops is not less than 6, the controller 103 turns-off camera power in step S18 and terminates the lens movement control operation.
As illustrated above, in the lens movement control method of the related art, after the bobbin 121 has dropped, the lens moves to the bottom surface. The foregoing procedure is repeated by the maximum number of bobbin 121 drops. This repetition procedure increases the operation time. As a result, it takes more than 6 seconds from when a camera enters a stop mode to a when the lens of the camera module moves to the bottom surface, which results in an error frequently occurring in the determining procedure.
Therefore, a need exists for a lens movement control method of a camera module having a short operation time capable of preventing the occurrence of an error and a VCA allophone, and an apparatus thereof.